diff --git a/lib/Diskstats.pm b/lib/Diskstats.pm
index d43a92c4..69dbf78a 100644
--- a/lib/Diskstats.pm
+++ b/lib/Diskstats.pm
@@ -93,29 +93,35 @@ sub new {
 # The next lot are accessors, plus some convenience functions.
 
 sub curr_ts {
-   my ($self, $val) = @_;
-   if ($val) {
-      $self->{_ts}->{curr} = $val;
-   }
+   my ($self) = @_;
    return $self->{_ts}->{curr} || 0;
 }
 
-sub prev_ts {
+sub set_curr_ts {
    my ($self, $val) = @_;
-   if ($val) {
-      $self->{_ts}->{prev} = $val;
-   }
+   $self->{_ts}->{curr} = $val || 0;
+}
+
+sub prev_ts {
+   my ($self) = @_;
    return $self->{_ts}->{prev} || 0;
 }
 
-sub first_ts {
+sub set_prev_ts {
    my ($self, $val) = @_;
-   if ($val) {
-      $self->{_ts}->{first} = $val;
-   }
+   $self->{_ts}->{prev} = $val || 0;
+}
+
+sub first_ts {
+   my ($self) = @_;
    return $self->{_ts}->{first} || 0;
 }
 
+sub set_first_ts {
+   my ($self, $val) = @_;
+   $self->{_ts}->{first} = $val || 0;
+}
+
 sub filter_zeroed_rows {
    my ($self, $new_val) = @_;
    if ( defined($new_val) ) {
@@ -306,7 +312,7 @@ sub _save_curr_as_prev {
          $self->{_prev_stats_for}->{$dev}->{sum_ios_in_progress} +=
             $curr->{$dev}->{ios_in_progress};
       }
-      $self->prev_ts($self->curr_ts());
+      $self->set_prev_ts($self->curr_ts());
    }
 
    return;
@@ -321,7 +327,7 @@ sub _save_curr_as_first {
          # be enough.
          map { $_ => {%{$curr->{$_}}} } keys %$curr
       };
-      $self->first_ts($self->curr_ts());
+      $self->set_first_ts($self->curr_ts());
       $self->{_first} = undef;
    }
 }
@@ -627,7 +633,7 @@ sub _load {
          if ( $current_ts && %$new_cur ) {
             $self->_save_curr_as_prev( $self->stats_for() );
             $self->_save_stats($new_cur);
-            $self->curr_ts($current_ts);
+            $self->set_curr_ts($current_ts);
             $self->_save_curr_as_first( $new_cur );
             $new_cur = {};
          }
@@ -646,7 +652,7 @@ sub _load {
       if ( %{$new_cur} ) {
          $self->_save_curr_as_prev( $self->stats_for() );
          $self->_save_stats($new_cur);
-         $self->curr_ts($current_ts);
+         $self->set_curr_ts($current_ts);
          $self->_save_curr_as_first( $new_cur );
          $new_cur = {};
       }
diff --git a/lib/DiskstatsGroupByAll.pm b/lib/DiskstatsGroupByAll.pm
index 526a6a64..a21bf804 100644
--- a/lib/DiskstatsGroupByAll.pm
+++ b/lib/DiskstatsGroupByAll.pm
@@ -64,7 +64,7 @@ sub group_by_all {
             },
          map( { ($_ => $args{$_}) } qw(filehandle filename data) ),
       );
-      if (!$self->prev_ts) {
+      if (!$self->prev_ts()) {
          seek $args{filehandle}, $orig, 0;
       }
       return;
diff --git a/t/lib/Diskstats.t b/t/lib/Diskstats.t
index 3e931358..4d7e4bb8 100644
--- a/t/lib/Diskstats.t
+++ b/t/lib/Diskstats.t
@@ -168,15 +168,16 @@ throws_ok( sub { $obj->design_print_formats( columns => {} ) },
         qr/The columns argument to design_print_formats should be an arrayref/,
         "design_print_formats dies when passed an invalid columns argument");
 
-for my $meth ( qw( curr_ts prev_ts first_ts ) ) {
-   ok(!$obj->$meth(), "Diskstats->$meth is initially false");
+for my $method ( qw( curr_ts prev_ts first_ts ) ) {
+   my $setter = "set_$method";
+   ok(!$obj->$method(), "Diskstats->$method is initially false");
 
-   $obj->$meth(10);
-   is($obj->$meth(), 10, "Diskstats->$meth(10) sets it to 10");
+   $obj->$setter(10);
+   is($obj->$method(), 10, "Diskstats->$setter(10) sets it to 10");
 
-   $obj->$meth(20);
+   $obj->$setter(20);
    $obj->clear_ts();
-   ok(!$obj->$meth(), "Diskstats->clear_ts does as advertized");
+   ok(!$obj->$method(), "Diskstats->clear_ts does as advertized");
 }
 
 is($obj->out_fh(), \*STDOUT, "by default, outputs to STDOUT");
@@ -371,9 +372,9 @@ EOF
       );
    }
 
-   $obj->curr_ts(0);
-   $obj->prev_ts(0);
-   $obj->first_ts(0);
+   $obj->set_curr_ts(0);
+   $obj->set_prev_ts(0);
+   $obj->set_first_ts(0);
 
    throws_ok(
       sub { $obj->_calc_deltas() },